The incorporation of flavorants in tobacco products is an important development in the tobacco industry due to the lowered aromaticity of the available tobacco and the increased preference of smokers for filter cigarettes and low delivery cigarettes. The addition of certain desirable flavorants to tobacco is limited by their volatility, which causes them to be lost or diminished in quantity during processing and storage of the tobacco product. This problem is even more acute for filter cigarettes containing an active adsorbent, such as charcoal, in the filters. During the processing and storage of this type of product, volatile flavorants have a tendency to migrate from the tobacco and may be irreversibly bound by the active adsorbent thereby partially or completely depleting the flavorant in the product and possibly altering the effectiveness of the acute adsorbent in its selective removal of undesirable smoke components.
The use of carboxylic acid flavorants for tobacco products has received acceptance because of the desirable aroma and flavor characteristics which they impart to the smoke (J. C. Leffingwell, H. J. Young, and E. Bernasek, "Tobacco Flavoring for Smoking Products," R. J. Reynolds Tobacco Company, Winston-Salem, 1972). Specifically, acetic acid is commonly used as an ingredient of a Latakia tobacco flavoring formulation (J. Merory, "Food Flavorings," AVI Publishing Company, Incorporated, Westport, Connecticut, page 420, 1968). Isovaleric acid and 3-methylvaleric acid are major ingredients in a Turkish tobacco flavor formulation (R. H. Stedman and C. D. Stills, U.S. Pat. No. 3,180,340). Desirable flavors have been imparted to cigarette smoke by the addition of 4-ketoacids to tobacco (W. A. Rohde, U.S. Pat. No. 3,313,307).
Numerous methods of adding flavorants to tobacco smoke are known. However, none of the known methods has been found to be completely satisfactory, particularly when the flavorant is a low molecular weight carboxylic acid. Specifically, some of these acids are highly volatile and possess objectionably strong odors that render them difficult to use in bulk amounts required for manufacturing purposes. In addition, some of the volatile acids may impart an undesirable pack aroma.
In an attempt to alleviate some of these problems, carboxylic acids have been incorporated in tobacco as part of a compound (i.e., an organic acid release agent) in such form that upon burning of the tobacco the compound will liberate one or more organic acids imparting a selected and desired flavor and aroma to the smoke. While considerably more satisfactory then earlier attempts, even this technique has evidenced certain drawbacks.
For example, U.S. Pat. Nos. 2,766,145 through 2,766,150 describe a variety of methods for treating tobacco with compounds that release carboxylic acids on pyrolysis. The 2,766,146 patent describes esters of polyhydroxy compounds as additives for tobacco; however, these esters are still sufficiently volatile to distill down a cigarette rod before appreciable pyrolysis and release of the desired carboxylic acid occurs.
U.S. Pat. No. 2,766,150 describes nonvolatile synthetic polymers or condensation products, preferably those related to polyvinyl alcohol and vinyl alcohol-type condensation products. On pyrolysis, the carboxylic acid is liberated to flavor the smoke. These polymers have a distinct disadvantage in that they generally have high molecular weights and are more difficult to solubilize for application on tobacco.
Flavor release technology with respect to menthol has received much attention in recent years, and various approaches have been suggested in an attempt to solve the problem of retaining menthol in tobacco and achieving an even and quantitative delivery of menthol in the smoke.
U.S. Pat. Nos. 3,886,603 and 4,002,179 describe the development of a new type of menthol-release agent for imparting menthol flavor to tobacco smoke. The menthol-release agent is a polymeric l-menthyl carbonate ester composition characterized by the presence of a tertiary alcohol ester attachment. Other types of polymeric flavorant release resins, which have been described recently, are prepared by the polymerization of an .alpha.-substituted-vinyl carbonate ester and are specifically designed to release alcohol flavorants on pyrolysis.
Many of the flavorant-release methods mentioned hereinabove suffer certain disadvantages, such as premature release of the flavorant, low transfer to mainstream smoke, and, in some instances, undesirable off-taste or flavor in the tobacco smoke.
Accordingly, it is a main object of this invention to provide a tobacco flavorant that is characterized by lack of mobility and/or volatility at ambient temperature when incorporated in a tobacco composition.
It is another object of this invention to provide a polymeric composition that is adapted to release carboxylic acid flavorant of enhancing character to tobacco smoke under normal smoking conditions with optimal efficiency and without masking of the natural flavor of the resultant main stream tobacco smoke.
It is a further object of this invention to provide a polymeric composition that is adapted to release carboxylic acids to tobacco smoke under normal smoking conditions with nondeleterious effect on the flavor of the resultant tobacco smoke.
It is yet a further object of this invention to provide polymeric compositions that are stable under normal manufacturing processes and that will not impart an undesirable aroma to the tobacco or to a pack of cigarettes.
Other objects and advantages of the present invention shall become apparent from the following description and examples.